/*
 * Copyright 2019 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "modules/skottie/src/effects/Effects.h"

#include "include/effects/SkRuntimeEffect.h"
#include "include/private/base/SkTPin.h"
#include "modules/skottie/src/SkottieJson.h"
#include "modules/skottie/src/SkottieValue.h"
#include "modules/sksg/include/SkSGColorFilter.h"
#include "src/utils/SkJSON.h"

namespace skottie::internal {
namespace {
// AE Saturation semantics:
//
//   - saturation is applied as a component-wise scale (interpolation/extrapolation)
//     relative to chroma mid point
//   - the scale factor is clamped such that none of the components over/under saturates
//     (e.g. below G/R and B are constrained to low_range and high_range, respectively)
//   - the scale is also clammped to a maximum value of 126, empirically
//   - the control is mapped linearly when desaturating, and non-linearly (1/1-S) when saturating
//
// 0               G    R                  B                                   1
// |---------------+----+------------------+-----------------------------------|
//                 |           |           |
//                min         mid         max
//                  <------- chroma ------>
//  <------- low_range -------> <---------------- high_range ----------------->
//
// With some care, we can stay in premul for these calculations.
static constexpr char gSaturateSkSL[] = "uniform half u_scale;"

    "half4 main(half4 c) {"
    // component min/max
    "half2 rg_srt = (c.r < c.g) ? c.rg : c.gr;"
    "half c_min = min(rg_srt.x, c.b),"
    "c_max = max(rg_srt.y, c.b),"

    // chroma and mid-chroma (epsilon to avoid blowing up in the division below)
    "ch     = max(c_max - c_min, 0.0001),"
    "ch_mid = (c_min + c_max)*0.5,"

    // clamp scale to the maximum value which doesn't over/under saturate individual components
    "scale_max = min(ch_mid, c.a - ch_mid)/ch*2,"
    "scale = min(u_scale, scale_max);"

    // lerp
    "c.rgb = ch_mid + (c.rgb - ch_mid)*scale;"

    "return c;"
    "}";

static sk_sp<SkColorFilter> make_saturate(float chroma_scale)
{
    static const auto *effect = SkRuntimeEffect::MakeForColorFilter(SkString(gSaturateSkSL), {}).effect.release();
    SkASSERT(effect);

    return effect->makeColorFilter(SkData::MakeWithCopy(&chroma_scale, sizeof(chroma_scale)));
}

class HueSaturationEffectAdapter final : public AnimatablePropertyContainer {
public:
    static sk_sp<HueSaturationEffectAdapter> Make(const skjson::ArrayValue &jprops, sk_sp<sksg::RenderNode> layer,
        const AnimationBuilder *abuilder)
    {
        return sk_sp<HueSaturationEffectAdapter>(new HueSaturationEffectAdapter(jprops, std::move(layer), abuilder));
    }

    const sk_sp<sksg::ExternalColorFilter> &node() const
    {
        return fColorFilter;
    }

private:
    HueSaturationEffectAdapter(const skjson::ArrayValue &jprops, sk_sp<sksg::RenderNode> layer,
        const AnimationBuilder *abuilder)
        : fColorFilter(sksg::ExternalColorFilter::Make(std::move(layer)))
    {
        enum : size_t {
            kChannelControl_Index = 0,
            kChannelRange_Index = 1,
            kMasterHue_Index = 2,
            kMasterSat_Index = 3,
            kMasterLightness_Index = 4,
            kColorize_Index = 5,
            kColorizeHue_Index = 6,
            kColorizeSat_Index = 7,
            kColorizeLightness_Index = 8,
        };

        EffectBinder(jprops, *abuilder, this)
            .bind(kChannelControl_Index, fChanCtrl)
            .bind(kMasterHue_Index, fMasterHue)
            .bind(kMasterSat_Index, fMasterSat)
            .bind(kMasterLightness_Index, fMasterLight);

        // TODO: colorize support?
    }

    void onSync() override
    {
        fColorFilter->setColorFilter(this->makeColorFilter());
    }

    sk_sp<SkColorFilter> makeColorFilter() const
    {
        enum : uint8_t {
            kMaster_Chan = 0x01,
            kReds_Chan = 0x02,
            kYellows_Chan = 0x03,
            kGreens_Chan = 0x04,
            kCyans_Chan = 0x05,
            kBlues_Chan = 0x06,
            kMagentas_Chan = 0x07,
        };

        // We only support master channel controls at this point.
        if (static_cast<int>(fChanCtrl) != kMaster_Chan) {
            return nullptr;
        }

        sk_sp<SkColorFilter> cf;

        if (!SkScalarNearlyZero(fMasterHue)) {
            // Linear control mapping hue(degrees) -> hue offset]
            const auto h = fMasterHue / 360;

            const float cm[20] = {
                1, 0, 0, 0, h,
                0, 1, 0, 0, 0,
                0, 0, 1, 0, 0,
                0, 0, 0, 1, 0,
            };

            cf = SkColorFilters::HSLAMatrix(cm);
        }

        if (!SkScalarNearlyZero(fMasterSat)) {
            // AE clamps the max chroma scale to this value.
            static constexpr auto kMaxScale = 126.0f;

            // Control mapping:
            //   * sat [-100 .. 0) -> scale [0 .. 1)   , linear
            //   * sat  [0 .. 100] -> scale [1 .. max] , nonlinear: 100/(100 - sat)
            const auto s = SkTPin(fMasterSat / 100, -1.0f, 1.0f),
                       chroma_scale = s < 0 ? s + 1 : std::min(1 / (1 - s), kMaxScale);

            cf = SkColorFilters::Compose(std::move(cf), make_saturate(chroma_scale));
        }

        if (!SkScalarNearlyZero(fMasterLight)) {
            // AE implements Lightness as a component-wise interpolation to 0 (for L < 0),
            // or 1 (for L > 0).
            //
            // Control mapping:
            //   * lightness [-100 .. 0) -> lerp[0 .. 1) from 0, linear
            //   * lightness  [0 .. 100] -> lerp[1 .. 0] from 1, linear
            const auto l = SkTPin(fMasterLight / 100, -1.0f, 1.0f),
                       ls = 1 - std::abs(l), // scale
                lo = l < 0 ? 0 : 1 - ls;     // offset

            const float cm[20] = {
                ls,  0,  0, 0, lo,
                 0, ls,  0, 0, lo,
                 0,  0, ls, 0, lo,
                 0,  0,  0, 1,  0,
            };

            cf = SkColorFilters::Compose(std::move(cf), SkColorFilters::Matrix(cm));
        }

        return cf;
    }

    const sk_sp<sksg::ExternalColorFilter> fColorFilter;

    float fChanCtrl = 0.0f, fMasterHue = 0.0f, fMasterSat = 0.0f, fMasterLight = 0.0f;
};
} // namespace

sk_sp<sksg::RenderNode> EffectBuilder::attachHueSaturationEffect(const skjson::ArrayValue &jprops,
    sk_sp<sksg::RenderNode> layer) const
{
    return fBuilder->attachDiscardableAdapter<HueSaturationEffectAdapter>(jprops, std::move(layer), fBuilder);
}
} // namespace skottie::internal
